1. Field of the Invention
The present invention concerns an ultra-rapid digitally controlled electronic camera for the study of extremely brief light phenomena.
Said camera is used to record images of extremely short duration, to record a profile of the evolution in time of extremely brief light phenomena. The camera is particularly applicable to ballistics, explosives, the study of living cells, laser experiments, etc.
An ultra rapid electronic camera with a scanning aperture for studying light phenomena is already known, utilizing a bilamellar optical image converting tube, such as that described in French Pat. No. 2 561 441. Said tube is associated with different means for supplying its electrodes at high electrical voltage and with a means for recording the image of the aperture appearing on the screen. The recording device may be, for example, a photographic plate.
The bilamellar image converting tube described in the patent cited above requires use of different high voltage electrical sources of fixed or adjustable values.
2. Description of the Related Art
Refer to FIG. 1 for a perspective drawing of the component arrangement of a prior art electronic camera.
As shown, the tube comprises in succession along axis OZ, a plane photocathode 1 perpendicular to said axis, bordered by a narrow aperture 2 for receiving photons 3 from the phenomena being studied, and which emits electrons 4.
Said tube also comprises a pair of plane electrodes 5 for extracting and accelerating electrons, said electrodes being parallel to the aperture and to axis OZ.
The photocathode 1 is connected to an electrical supply source 14 of continuous high voltage and fixed value of 15,000 VDC, for example, in relation to reference mass M.
Electrodes 5 are electron accelerating electrodes; they are connected to reference mass M.
The beam thus accelerated along axis OZ perpendicular to the photocathode arrives at quadrupolar spatial focusing lens 6, 7. Said lens comprises a first and a second pair of cylindrical electrodes 6, 7 parallel to axis OZ and respectively parallel and perpendicular to aperture 2. The first pair of 6 electrodes in said lens is connected to a constant voltage electrical supply source 15 of approximately +400 VDC, for example. The second pair of electrodes 7 in said quadrupolar lens is connected to a constant high voltage electrical supply source 16 of approximately -400 VDC, for example. The camera also comprises a temporal focusing lens consisting of at least a first, a second and a third pair of electrodes 8, 9A, 9B, 10. One electrode 9A of the second pair is connected to an adjustable high voltage source 17 of, for example, between 0 and -10 000 VDC. One electrode 9B of said second pair is connected to a high voltage, adjustable electrical source 18, for example, between 0 and -10,000 VDC. Said pair of electrodes 9A-9B comprises means for deflecting the beam onto screen 11. The first and third pairs of electrodes 8, 10 are connected to reference mass M. In this known type of camera, electrodes 9A-9B are deflection electrodes. They are also connected to fixed value electrical voltage sources 19, 20 by a deflection regulating means 21.
A screen 11 displays image 12 from the aperture
Devices 13 for recording image 12 from the aperture onto screen 11 are associated with this prior art camera. Said recording devices may consist of a photographic plate 13, for example.
The functioning of this prior art camera will now be described in a succinct manner; photocathode 1 emits electrons into a zone defined by aperture 2, said electrons being produced by the impact of photons 3 on said photocathode. These electrons are accelerated by the pair 5 of acceleration electrodes. the electrodes of the first pair 6 of the quadrupolar lens allow the image to be captured through the aperture on temporal plane yoz. The electrodes of the second pair 7 of said quadrupolar lens are for spatial representation through the aperture onto plane XOZ parallel to the aperture and perpendicular to the photocathode. Electrodes 6 of the quadrupolar lens cause the beam to diverse; it is refocused by means of electrodes 8, 9A-9B, 10 of the temporal focusing lens. Electrodes 9A-9B cause temporal deflection of the beam onto plane YOZ.
An ultra rapid electronic camera using the tube of FIG. 1 and which utilizes both fixed and adjustable voltage value sources has one important disadvantage: when one wishes to study a light phenomena, one must pre-adjust the high voltage furnished by the adjustable sources before studying the phenomena, these high voltages being measured by a means temporarily connected to the source outlets during adjustment. The voltage measurement devices are then disconnected and study of the phenomena may begin; thereafter, it is impossible to alter the voltage adjustment values during the course of the experiment. It is also impossible to monitor the voltage values supplied to different electrodes constantly throughout the experiment because the measurement devices are disconnected once voltage regulation has been accomplished. Furthermore, the prior art tube used in this camera has no electrode for temporal prefocusing in front of the quadrupolar lens, thereby detracting from the camera's performance.